Quantum entanglement and quantum computing in the optical frequency comb

An ultrafast laser emits over a vastly multimode gain spectral bandwidth — an optical frequency comb, or OFC — but the emission happens but one photon at a time, albeit in a stimulated manner. When one changes the gain medium from linear (one-photon) to nonlinear (two-photon), the laser becomes a two-photon laser (if the pump excites the gain medium) or an optical parametric oscillator (if it doesn't) and two-photon emission leads to massive multipartite entanglement of the OFC modes, which has been demonstrated experimentally. I will explain how this entanglement can be harnessed and leveraged toward building a universal quantum computer.\\ \\ Reference: M. Chen, N. C. Menicucci, and O. Pfister, ``Experimental realization of multipartite entanglement of 60 modes of a quantum optical frequency comb,'' \textit{Physical Review Letters} \textbf{112}, 120505 (2014).\\ \\ DOI: http://doi.org/10.1103/PhysRevLett.112.120505